Michael Nolan said: "It's not who we are that holds us back, it's who we think we're not".
The way in which we as human beings perceive (see) things around us influences the way in which we see ourselves and the world around us. Therefore be aware, because you (and I) deal with life according to how we see things. The way in which we see things (in other words our perceptions) is shaped by things from our childhood, for example the way in which our parents disciplined us. Our perceptions are also influenced by the values, meanings and norms of people around us, for example friends, teachers, the social media, colleuages, etcetera.
A practical example of different ways to see the same thing is:
Thabo and Jakes were both retrenched from their jobs. Thabo experiences it as the worst thing that ever happened to him and he believed that his life was over and that nothing good could ever come from his retrenchment. He became a bitter man and felt sorry for himself for the rest of his life.
On the other hand Jakes was shocked and stunned just like Thabo was, but he decided that something good has to come from his retrenchment. Therefore Thabo started to look for new opportunities, met up with people who could support him and at the end started his own business which did way better than he did in his job from which he had been retrenched.
So, don't hold yourself back, for you are enough, you are a fighter and you are going to make your dreams come true if you start to belief in yourself. Then you learn what mental toughness really is!